The invention concerns an external shell of a centrifugal flow pump wheel of a hydrodynamic flow unit and its method of making, wherein the shell has a toroidal internal surface, a constant wall thickness in its central region, and an integral connecting sleeve portion with a centering surface connected to a fastening surface portion with a centering surface connected to a fastening surface at its outside region.
In known triple location converter (Design Books No. 21 "Fottinger-Kupplungen und Fottiner-Getriebe" by Dipl.-Ing. E. Kickbusch; Springer-Verlag Berlin/Gottingen/Heidelberg 1963; Page 1, FIG. 1/1), an external shell of the type mentioned at the beginning is designed as a heavy cast part in which the fastening surface is located in a radial plane, normal to the axis of rotation, of a flange section. This flange section has bolt penetrations radially outside a centering surface and located parallel to the axis of rotation for the bolt fastening to the mating flange of the drive-side converter cover. Whereas the wall thickness in the region between the flange section having the bolt penetrations and the entry-side connecting sleeve of this known outer shell remains substantially constant, its wall thickness in the region of the centering surface is reduced because the drive torque is introduced into the pump wheel via the radial flange section having the bolt penetrations. This gives an undesirably large converter external diameter. However, in this known external shell, a sharp-edged transition between the outlet-side end of the inner surface and an end surface located in a radial plane normal to the axis of rotation of the outlet-side connecting sleeve is already provided so that it can be assumed that the flow losses at the transition between the pump and turbine wheels are kept small.
The subject matter of an unpublished German patent application shows a spoke for connecting a wheel hub with an outer ring of a drive spoke wheel for a hydrodynamic torque converter. The internal shell of the centrifugal flow pump wheel is connected, for the purpose of distributing the power, by means of a rotating spring connection located in the internal toroid which has no flow, to the outer ring. The external shell of the pump wheel is attached by a weld connection to the mating sleeve, overlapping the outlet-side connecting sleeve of the shell with cylindrical shaping of the centering surface and the fastening surface, of a drive-side converter cover. No information is given in the patent application with respect to the material and manufacture of the external shell.
An object of which the instant invention is based, consists essentially in providing a sharp-edged transition at the outlet-side end of the inner surface to a radial end surface of the connecting sleeve, in an outer shell of a centrifugal flow pump wheel while keeping weight and dimensions small.
In an external shell of a centrifugal flow pump wheel of a hydrodynamic flow unit having a toroidal internal surface and a constant wall thickness in its central region and with an integral connecting sleeve portion at its outlet-side region and with the integral connecting sleeve portion having a cylindrical centering surface and a fastening surface extending from the centering surface, an external shell according to the instant invention is obtained by having: (1) the external shell being formed from a sheet metal pressed part; (2) the connecting sleeve being created by upsettingly deforming the sheet metal part wherein the fastening surface is given a cylindrical shape and the centering surface is machined to its required diameter (27) after being upsettingly deformed; (3) the required diameter being greater by twice the constant wall thickness than the diameter, of a reference circle centered about the axis of rotation of the external shell of the hydrodynamic flow unit (14--14); and wherein (4) the circle is defined by the intersection (15) of the internal toroidal surface (7) with a reference plane (17--17) normal to the axis of rotation of the external shell and containing the center (16) of the internal toroidal surface (7).
Additional advantageous embodiments of the external shell in accordance with the invention are obtained by only having a portion of the wall thickness upsettingly deformed. Also advantageous is the locating of a strip groove concentric with the axis of rotation of the shell.
The following advantages are achieved by means of the invention:
Because of the sheet metal pressed part design, the manufacture of the external shell is made cheaper and its weight is kept low; and the wall thickness between the centering surface and the internal surface is substantially greater than the normal wall thickness of the external shell, whose length is additionally increased by upsettingly deforming procedure.
In order to increase the strength and stiffness of the external shell/converter cover structural unit, the invention contemplates that the mating sleeve of a torque converter cover overlaps both a centering surface and a fastening surface at the connecting sleeve of an external shell of the torque converter and is then fixed by a weld seam between the fastening surface and an end of the cover.
These measures achieve the effect that the otherwise conventional means of compensating for the axial clearance between a radially inner hub flange of a torque converter cover and a radially inner, i.e., entry-side, connecting sleeve of the outer shell of the torque converter pump wheel become unnecessary, because hydraulic pressures in the torque converter can no longer have the effect of causing marked "stretching" of the structural unit mentioned - as occurs in the case of known converters or couplings.
The invention provides for maintaining circularity of the outer shell of the torque converter pump wheel or admitting of only a slight loss of circularity even after a brazing fastening procedure of the pump vanes to the pump shell and thus out-of-balance of the converter, is therefore reduced.
The sharp-edged nature of the outlet-side end of the internal surface of the pump shell of the torque converter is also ensured in the external shell according to the invention by upsettingly deforming procedure and/or by turning over of the connecting sleeve.
The retention of the shape of the sheet metal pressed part during the upsettingly deforming process is facilitated by stop grooves in the external surface of the external shell. The expedient of using only part of the wall thickness of the external shell of the torque converter pump for forming the connecting sleeve by upsettingly deforming, also leads to smaller upsetting forces and therefore easier retention of the shape of the sheet metal pressed part during the upsettingly deforming procedure.
These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purposes of illustration only, plural embodiments in accordance with the present invention, and wherein: